The present invention relates to a crawler vehicle commonly referred to as a bulldozer, and, more particularly, to a crawler vehicle having oscillating track carriages. More specifically, the present invention relates to a vehicle having a longitudinal axis, a supporting frame, and two longitudinal carriages located on opposite sides of the frame.
The carriages support respective tracks for driving the vehicle, and are connected to the frame by respective rear pivots to rotate about a rear transverse axis and in a substantially vertical oscillating plane in dependence of the roughness of the ground over which the vehicle travels.
In vehicles of the type described above, the front end of each carriage commonly is connected to the frame by a vertical guide for guiding the movement of the carriage in the oscillating plane.
Given the rough conditions, particularly in terms of dust and mud, in which known crawler vehicles of the above type operate, the guides connecting the front ends of the carriages are subjected to severe wear and damage, and therefore call for continual maintenance and frequent replacement.
In an alternative solution, the front ends of the carriages are connected to each other by a front cross member, a central portion of which is hinged to the vehicle frame to rotate about a hinge axis parallel to the longitudinal axis. More specifically, each end of the cross member is hinged to the respective carriage by a cylindrical hinge pin perpendicular to the rear transverse axis.
This solution is also unsatisfactory on account of the severe and potentially dangerous bending and/or torsional stress to which the carriages, rear hinges and front hinge pins are subjected when operating over rough ground causing one carriage to rotate upwards and the other downwards in their respective oscillating planes.
In fact, as the carriages rotate increasingly in opposite directions about the rear transverse axis, the distance between the front ends of the carriages increases, whereas the front ends remain connected substantially rigidly to each other by the cross member, which thus generates stress and consequently strain on the carriages and, indirectly, on the rear hinges.
It is an object of the present invention to provide a crawler vehicle with oscillating track carriages, designed to provide a straightforward, low-cost solution to the aforementioned drawbacks.
According to the present invention, there is provided a crawler vehicle having a frame extending along a longitudinal axis; two track carriages on opposite sides of said frame; a first connecting device interposed between the carriage and the frame to permit oscillation of each carriage, with respect to the frame, about at least a first hinge axis extending perpendicularly to the longitudinal axis; a connecting cross member oriented substantially parallel to the first hinge axis; and a second connecting device interposed between the cross member and each carriage to permit relative oscillation of the cross member and the carriage about a second hinge axis extending perpendicularly to the first hinge axis.
The crawler vehicle includes a compensating mechanism for varying the length of the cross member between two given values as the carriages oscillate about the first hinge axis.
These and other objects, features and advantages are accomplished according to the instant invention in which a crawler vehicle has a frame extending along a longitudinal axis of the vehicle, and two lateral track carriages oscillating with respect to the frame about a rear transverse axis. Each carriage is connected to a front cross member by a respective connecting assembly having a pin, which permits relative oscillation of the cross member and the carriage about a hinge axis perpendicular to the rear transverse axis, and has an eccentric portion for varying the size of the cross member between two given values as the carriages oscillate about the rear transverse axis.